Whitefly, techniques and organic treatments to avoid it
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Turn a hibiscus or tomato leaf over and you may find it crowded with minute white insects, sucking sap until the foliage turns sticky and black with sooty mould. Whitefly weakens plants and, in a large enough invasion, can kill them; since the colonies need heat to develop, keeping plants cool is what turns the tide.
After forming a large colony under the leaves, these insects suck the sap of the plant and weaken it. They also make leaves sticky and cause sooty mold to appear.
A large-scale invasion can even lead to the plant’s demise.
Conditions that favor the spread of whitefly
Greenhouse heat and single-crop expanses favour whitefly outbreaks
The main causes of whitefly appearing on plants are:
Whitefly can be met with a spray, a trap, a predator, or simply a drop in temperature. Here is what each option acts on before you commit to one.
Whitefly controls compared
Control
Type
What it acts on
Practical notes
Insecticides or aphid treatments
Chemical spray
Adult insects only — eggs survive
Repeat every 3 days for 2 to 3 weeks; the fumes are dangerous to breathe in
Yellow sticky traps
Trapping
Flying adults
Sticky glue on any yellow surface, sold in horticulture stores
Encarsia formosa
Parasitoid wasp
Whitefly larvae, in which it lays its eggs
Not to be used indoors
Macrolophus caliginosus
Predatory bug
Eats the whiteflies themselves
Not to be used indoors
Insecticidal soap with permethrin
Organic spray
Insects on the leaves
Proven efficient
Moving plants to a cool room
Cultural measure
Removes the heat the parasites need
Combines with any of the treatments above
Whatever you spray or release, shifting the infected plant somewhere cool works alongside it.
How to fight whiteflies?
Sprays kill the adults but leave the eggs behind
Traditional methods like insecticides or aphid treatments can be effective, even though they only target adult insects and don’t destroy eggs.
If those methods are applied, repeat treatment every 3 days over a 2 to 3 week period. Be careful! These products are often dangerous to breath in.
Organic treatments against whitefly
Whiteflies are drawn to yellow, so traps use it
Place whitefly traps. In specialized horticulture stores, you can find sticky glue that can be applied on any yellow surface, since whiteflies are attracted by that color.
Some predator insects can help eliminate them. A tiny wasp called Encarsia formosa does just that, since it lays its eggs inside whitefly larvae. Another predator is a bug called Macrolophus caliginosus that eats these parasites.
Don’t use predator insects inside your house.
Lastly, it is also possible to spray an insecticidal soap based on permethrin. This last solution has been proven to be efficient.
In all above cases, you can bring infected plants to a cool room since these parasites need heat to develop.
Images: CC BY 4.0: Mihajlo Tomić; own work: Rosalyn & Gaspard Lorthiois; Public Domain: Hugo Hulsberg, Scot Nelson
Written by Gaspard Lorthiois | Loves helping out, especially when it comes to growing things. Worked in herbal medicine, runs a farm, and dabbles in tech. Master's degree and engineer.
